It may seem surprising that after three decades of 'early music' research, critical discoveries can still be made about a great composer such as Mozart - particularly discoveries around his well-known masterpieces. This recording presents the premiere recording of the Grande Sonate, an anonymous arrangement for fortepiano and basset clarinet of Mozart's beloved Clarinet Quintet in A major, K. 581. Both the Clarinet Quintet and the Concerto in A major, K. 622, were originally written for an instrument called the basset clarinet, which has four more chromatic notes at the bottom of its range than an ordinary clarinet. Since the manuscripts to both pieces were lost, clarinetists have had to make educated guesses about the passages that may have included these low notes. Significantly, this arrangement includes some of these basset notes, making it an important source for those wishing to restore the piece to its original form.